I have just started into my 5th season of doing tris and I seem to be lagging behind on the bike. My bike splits for short distance triathlons (10-40K) haven't improved at all since my second season. My first season I was new to endurance sports so I figured the rapid improvement between seasons 1 and 2 were just gains in general fitness. Some things I have tried that have not lead to any improvement include:
Currently I am biking 5x a week with a total of about 140km a week (one endurance ride of 60K plus 4 short interval rides of 20K). The interval rides are doing mostly at threshold pace or race pace. I haven't gone to aero wheels only because I am doing sprints (20K) and I didn't figure it was necessary for short course triathlons (are they?). I dropped my volume from 180K a week to 140K a week in favor of more intense bike sessions. I did this mainly because the added volume didn't have any effect on my bike splits.
I am at a bit of a loss with respect to my bike split performance, I thought in 3 years I should have seen some improvement in my race times but I haven't, this is not the case with the swim and the run where there has been noticeable improvement. Any advice would be much appreciated, thanks.